With the development of wireless communications technologies, significant progress has been made in the field of cellphones. The currently most popular type of cellphones are those of the so-called folding type that consist of two casings that can be rotated relative to each other and folded via a hinge in a direction such that the display unit and the input unit can be faced with each other. As compared with the initially employed straight type, the folding cellphones are foldable into a compact shape such that they can be easily carried around when not in use. This structure is very convenient as it allows the use of a large screen on the display unit for communications (see Patent Document 1, for example).    Patent Document 1: JP Patent Publication (Laid-Open) No. 06-037697 A (1994)